Methods for manufacturing corrugated perforated plastic tubes, particularly corrugated plastic tube made of a thermoplastic and particularly suited for drainage pipe, are known per se.
According to one of the known methods, a corrugated plastic tube which is corrugated in the transverse direction is externally supported by a sleeve-shaped guide, while cutters from the outer side of the plastic tube are active in the area in which the tube is externally supported, or outside this area where the tube is sufficiently rigid to stand the action of the punching means.
According to another known method, in punching helically profiled corrugated plastic tube, the sleeve-shaped guide is identically profiled as the plastic tube, so that when the sleeve-shaped guide is turning, the tube is simultaneously supported and conveyed.
Although these methods are satisfactory in many cases, the operative rate, i.e., the rate at which perforations can be made, is often not fast enough. With these methods one cannot work too fast because either the cutters in the shape of stamping knives form rough holes in the plastic tube, or, when a heated tube is used, no holes at all are made, because the tube of thermoplastic material is resilient along with the stamping knives so that no punching effect is produced.